Doctors trying to prevent recurrent miscarriages were misguided in looking only at women

Faulty sperm may be the reason why women suffer multiple miscarriages, scientists suspect, after finding that men whose partners struggle to carry a child to term have more DNA errors.

Researchers at Imperial College investigated the sperm quality of 50 men whose partners had experienced three or more consecutive miscarriages.

After comparing the results with the sperm health of 60 male volunteers whose partners had healthy pregnancies, they found the miscarriage group had twice as much damage to their DNA.

Dr Channa Jayasena, the lead author of the research, said: “Traditionally, doctors have focused attention on women when looking for the causes of recurrent miscarriage. The men’s health, and the health of their sperm, wasn’t analysed.

“However, this research adds to a growing body of evidence that suggests sperm health dictates the health of a pregnancy. For instance, previous research suggests sperm has an important role in the formation of the placenta, which is crucial for oxygen and nutrient supply to the foetus.”

Recurrent miscarriage, defined as the consecutive loss of three or more pregnancies before 20 weeks’ gestation, affects around one in 50 couples.

It has taken medicine a long time to realise sperm health has a role to play in miscarriage — and that the cause doesn’t lie solely with women

The research team said the DNA damage seen in sperm may be triggered by molecules known as reactive oxygen species, which form in semen and work to protect against bacteria infection. In high concentrations, they can have a harmful effect. The study found that sperm from men whose partners had suffered miscarriage had a fourfold increase in the amount of reactive oxygen species, compared with the control group.

Researchers are now investigating the potential factors that might trigger high levels of the usually helpful molecules, in the hope that they could limit their production in order to save pregnancies.

The experts said they suspected the molecules were being over-produced after previous infections. Dr Jayasena added: “Although none of the men in the trial had any ongoing infection, it is possible there may be other bacteria from previous infections lingering in the prostate gland, which makes semen. This may lead to permanently high levels of reactive oxygen species.

“It has taken medicine a long time to realise sperm health has a role to play in miscarriage — and that the cause doesn’t lie solely with women.

“Now we realise both partners contribute to recurrent miscarriage, we can hopefully get a clearer picture of the problem and start to look for ways of ensuring more pregnancies result in a healthy baby.”

The men in the miscarriage group were also older, with an average age of 37, compared with 30 in the control group, and slightly more overweight.

The study was carried out with couples who were patients at the recurrent miscarriage clinic at St Mary’s Hospital in London, part of the Imperial College Healthcare NHS Trust, and published in the journal Clinical Chemistry.